This invention relates to an improved tarpaulin cover system for open-top truck bodies.
Movable tarpaulin cover systems for truck boxes or trailers of the type including a floor, front wall and a pair of upright side walls and/or flatbed trailers are known in the prior art. See, for example Cramaro Canadian Patent No. 995,714 issued Aug. 24, 1976 and Biancale Canadian Patent No. 1,094,129 issued Jan. 20, 1981. In such systems, one end of a tarpaulin to cover the truck body is anchored to the front wall. A plurality of intermediate support bows extend in parallel fashion from side-to-side transversely across the truck body, the bows being secured at spaced locations to the tarpaulin. The ends of the intermediate bows are slidably secured on a movable cable for longitudinal movement with respect to the truck body. A lead bow extending parallel to the intermediate bows from side-to-side transversely across the truck body is secured to the free end of the tarpaulin. The ends of this bow are secured to the movable cable for movement therewith longitudinally with respect to the truck body. When the cable is moved in one direction, the lead bow and free end of the tarpaulin are drawn longitudinally to the back end of the truck body and the intermediate bows and tarpaulin are drawn proportionately rearwardly as required to covering the truck body. When the cable is moved in the opposite direction, the lead bow, intermediate bows and tarpaulin are retracted to the front end of the truck body to open position. In Biancale Canadian Patent No. 1,094,129, a single drive cable is provided with a pair of horizontal reaches of the cable extending along parallel to and above each of the upper edges of the box, the cable being in the form of a closed or endless loop mounted on pulleys attached to the truck box. A pair of the runs of the cable cross over each other from one side of the box to another in a region disposed below the upper edges of the box so that movement of the cable along its path causes each of the pair of horizontal reaches to move in the same direction relative to the upper edges of the box to effect movement of the tarpaulin. The cable is moved by means of a winch.
In Cramaro Canadian Patent No. 995,714, a pair of cables, one on each side of the truck box are provided, each cable providing one of the pair of horizontal reaches of the cable extending along parallel to and above each of the upper edges of the box. The two cables are simultaneously winched for movement.
Such conventional prior art systems have presented several problems in operation. Firstly, such systems have not reacted well to the winds generated during normal motion of the truck on which they have been installed. Such wind has caused the bows to bend out of position and cause wear and tear on the cable. As a result, the tarpaulin has required strapping to the truck body to keep it taut and in position. As well there is additional wear on the cable since the intermediate bows have their ends slidably secured to it.
Another danger exists if the drive cable on such a conventional system breaks. The tarpaulin and bow will then be released from the truck resulting in a potentially hazardous situation particularly if the truck is in transit.
U.S. Pat. No. 3,231,305 of Beckman issued Jan. 25, 1966 describes and illustrates a collapsible cover assembly for vehicles, on which the ends of the bows are mounted on sleeves which travel horizontally on a pair of rigid, tubular tracks mounted on either side of the truck body. While such a system may be suitable for a pick-up truck or the like, for which it was intended, it would not be suitable for a larger truck trailer. On larger truck trailer there would inevitably be a sag in the track which would make the sleeves very difficult or impossible to move. As well, such a system could not withstand the normal abuse to which a cargo trailer for a truck would be subject in loading and unloading, where inevitably such a track would occasionally be hit by the loading vehicle and bent or damaged, again further interfering with proper sliding of the sleeves.
Other patents of general background interest relating to tarpaulin cover systems for trucks are described and illustrated in Pickering et al U.S. Pat. No. 4,032,186 issued June 28, 1977 and Rodrigue Canadian Patent No. 1,107,790 issued Aug. 25, 1981.
It is an object of the present invention to provide an improved tarpaulin cover system for trucks which to some extent avoids or minimizes the problems of conventional systems with wind. It is a further object of the present invention to provide such a tarpaulin cover system for use on commerical truck bodies such as flat deck trailers and truck boxes, which system has increased safety.